NAND flash memories are known as non-volatile semiconductor memory devices which can be electrically rewritten and enable higher integration.
A memory cell of a NAND flash memory has a charge storage layer (floating gate) formed on a semiconductor substrate through a tunnel insulating film and a control gate which is laminated thereon through an inter-gate insulating film, and enables non-volatile storage of data in a charge storage state of the floating gate. For example, the memory cell stores binary data assuming that a threshold voltage is high when electrons are injected to the floating gate is data “0” and a threshold voltage is low when electrons in the floating gate are ejected is data “1”. The memory cell also enables multi-value storage such as quadrature storage or octal storage by further segmentalizing a threshold voltage distribution to be written.
However, there is a problem that, accompanying further miniaturization of memory cell arrays in recent years, an influence of an inter-cell interference between adjacent memories is increasing and thresholds of the adjacent memory cells also fluctuate when data is written in a selected memory cell. The same applies to charge trap non-volatile memories in which charge storage layers are formed with insulating films such as MONOS films.